A liquid crystal display panel includes two corresponding glass substrates, a thin-film transistor (TFT) substrate and a color filter (CF) substrate. Conventionally, the TFT on the TFT substrate comprise source contact, active layer and drain contact arranged laterally to form a planar device structure, in which the active layer or the conducting channel between the drain and source contacts is horizontal to the TFT substrate. Minimum length of the conducting channel is limited by the exposure resolution of the photolithography tool that is used. Current state-of-the-art photolithography doesn't allow the critical dimension (CD) of the conducting channel down to 3 μm or less.
The current trend of flat display panel is towards high resolution, so operational performance of the active switching devices will be more and more critical. For example, switching speed of the TFT has to be improved so as to be used in the display panel with a frame rate more than 120 Hz and a resolution more than 320 pixels per inch (PPI). To raise the switching frequency and to enlarge aperture ratio, length of the conducting channel in TFT must be further shortened. However, the planar-device-structure TFT is limited by the CD of the fabrication process. Therefore, it is in need to develop a new display panel.